新型磁性Mn0.6Zn0.4Fe2O4@CdS纳米复合光催化剂的制备及其吸附和光催化特性

以两步水(溶剂)热法制备了一种新型磁性Mn_(0.6)Zn_(0.4)Fe_2O_4@CdS纳米复合光催化剂,并采用X-射线衍射(XRD)、比表面(S_(BET))、扫描电镜-能谱(SEM-EDX)、紫外漫反射(UV-vis)、透射电镜(TEM)、磁滞回线(VSM)和价带能谱(VB-XPS)等手段对制备的铁氧体、CdS和复合材料进行了表征分析.结果发现,得到的材料元素含量与设计预期值吻合,纯相晶格参数与理论值匹配较高,特征峰证实复合材料中存在尖晶石铁氧体和CdS晶格;高分辨透射电镜(HR-TEM)分析表明,CdS有效地附着在铁氧体上,且在可见光区发生了红移.利用该材料对亚甲基蓝(MB)进行了暗室吸附和光催化活性的系统研究,结果表明,复合物吸附速率较快,适宜用Langmuir模型描述吸附平衡,最大吸附容量q_(max)高达79.6 mg·g~(-1);在测试的3个样品中,复合物光催化活性最高,经5次重复光催化实验,MB的降解率仍可保留在50%以上,且易磁分离回收;此外,通过自由基和空穴捕获实验、光致发光(PL)和电子顺磁共振(ESR)测试分析提出了MB降解机理.

Preparation of novel magnetic Mn0.6Zn0.4Fe2O4@CdS nanocomposite photocatalysts and its properties of adsorption and photocatalysis

A novel magnetic Mn_0.6Zn_0.4Fe₂O₄@CdS nano-composites (NPs) pholocatalyst is prepared via a two-step hydrothermal and solvothermal method. The as-prepared pholocatalyst samples are characterized using XRD, S_BET, SEM-EDX, UV-vis, TEM, VSM and VB-XPS. Test results show that the elements content of pure ferrite and CdS are in good agreement with the expected value, and theirs lattice parameters matches the theoretical value. The characteristic peaks corresponding to the spinel ferrite and CdS plane confirm the presence of both lattices in NPs. HR-TEM analysis also reveals the effective attachment of CdS onto the ferrite and red shift optical absorption spectra. In addition, the adsorption and photo-catalytic activities of the samples are systematically investigated by carrying out adsorbed and photo-degradation of methylene blue (MB) under dark adsorption and visible-light irradiation, respectively. Test results show that the adsorption rate of NPs is more faster, and it is suitable for Langmuir model to describe the adsorption equilibrium of MB by NPs, whose q_max is as high as 79.6 mg·g^-1. Comparing the results on three tested samples, the photocatalytic activity of NPs is the highest, and its degradation rate for MB could still be retained above 50% after 5 repeated experiments, which is easy to be recovered by magnetic separation. In addition, the degradation mechanism of MB is also proposed based on the investigation of free radical and hole scavengers experiments, PL and ESR.